Xanthenyl and thiaxanthenyl semicarbazides

ABSTRACT

4-(9-Xanthenyl)semicarbazide and thiosemicarbazide, 4-(9thiaxanthenyl)semicarbazide and thiosemicarbazide, and derivatives of these compounds, useful as antisecretory agents.

United States Patent Adams et al.

[451 May 27, 1975- XANTHENYL AND'THIAXANTHENYL SEMICARBAZIDES Inventors: Stewart Sanders Adams; Bernard John Armitage; Norman William Bristow; Bernard Vincent Heathcote, all of Nottingham, England Assignee: The Boots Company Limited,

Nottingham, England Filed: Dec. 12, 1973 Appl. No.: 423,925

Related U.S. Application Data Continuation of Ser. No. 277,360, Aug. 2, 1972, abandoned, which is a continuation-in-part of Ser. No. 858,183, Sept. 15, 1969, Pat. No. 3,686,218, which is a continuation-in-part of Ser. No. 662,987, Aug. 23, 1967, Pat. No. 3,644,420.

Foreign Application Priority Data Sept. 2, 1966 United Kingdom 39384/66 Apr. 5, 1967 United Kingdom... 15692/67 Sept. 27, 1968 United Kingdom 46085/68 U.S. Cl..... 260/293.58; 260/243 B; 260/243 R; 260/244 R; 260/247.1 P; 260/247.2 A;

260/256.4 l-l; 260/256.5 R; 260/268 TR; 260/293.57; 260/306.7; 260/307 F; 260/309.7; 260/310 D; 260/326.34; 260/328; 260/335; 424/246; 424/248; 424/250; 424/251; 4241/267; 424/270; 424/272; 424/273; 424/274; 424/275; 424/283 Primary Examiner-Henry R. Jiles Assistant Examiner-C. M. S. Jaisle Attorney, Agent, or FirmGordon W. Hueschen [57] ABSTRACT 4-(9-Xanthenyl)semicarbazide and thiosemicarbazide, 4-(9-thiaxantheny1)semicarbazide and thiosemicarbazide, and derivatives of these compounds, useful as antisecretory agents.

5 Claims, No Drawings XANTHENYL AND TI-IIAXANTHENYL SEMICARBAZIDES This is a continuation of application Ser. No. 277,360, filed Aug. 2, 1972, now abandoned, which application is a continuation-in-part of our copending application Ser. No. 858183, filed Sept. 15th 1969, now US. Pat. No. 3,686,218, which in turn is a continuation-in-part of our application Ser. No. 662987, filed Aug. 23rd 1967, now U.S. Pat. No. 3,644,420, the entire disclosure of which is incorporated herein by reference. The subject matter of this application was subjected to a requirement for restriction in application Ser. No. 858183, Paper No. 4.

This invention relates to new derivatives of xanthen and thiaxanthen which have valuable biological activity.

According to one feature of the invention there are provided compounds of formula I wherein Xn represents the group in which X and X are oxygen or sulphur;

the rings A and B may optionally contain substituents selected from halogen, alkyl, alkoxy and hydroxy;

R, is hydrogen, alkyl, substituted alkyl, alkenyl, cy-

cloalkyl, hydroxy, alkoxy, acyloxy or trialkylsilyloxy;

R is hydrogen, alkyl, substituted alkyl, alkenyl, cy-

cloalkyl, alkanoyl, or alkoxycarbonyl;

R is hydrogen, alkyl, substituted alkyl, alkenyl, cy-

cloalkyl, or alkoxy;

R is hydrogen, alkyl, substituted alkyl, alkenyl, cy-

cloalkyl, alkanoyl, or alkoxycarbonyl;

or R and R taken together represent (CH where m is 3 or 4, and one of the CI-I groups may be replaced by CO;

or R and R together with the nitrogen atom to which they are attached form a saturated 5-7 membered heterocyclic ring, optionally containing an additional hetero group selected from NH, O, S or N-lower alkyl; together with pharmaceutically acceptable acid addition salts of compounds of formula I; and, when R, and R each represent alkyl, substituted alkyl, or alkenyl, or together form a ring as hereinbefore defined, pharmaceutically acceptable quaternary salts of compounds of formula I.

The term substituted alkyl includes alkyl radicals containing substituents such as hydroxy, halogen, amino, alkanoylamino, alkoxycarbonylamino, alkylamino, alkanoyl(alkyl)amino, alkoxycarbonyl(alkyl- )amino, dialkylamino, aryl, aryloxy, alkoxy, acyloxy, and carboxy (in free acid, salt or ester form).

Alkanoyl and alkoxycarbonyl preferably indicate such groups containing up to 8 carbon atoms.

Acyl indicates the acyl residue of a carboxylic acid; such acids include aliphatic carboxylic acids, preferably C aromatic carboxylic acids, heterocyclic carboxylic acids, carbonic acids, N-alkylcarbamic acids, N,N-dialkylcarbamic acids, N-phenylcarbamic acid, N,N-tetramethylene carbamic acid, N,N-pentamethylenecarbamic acid, N,N-3-oxapentamethylenecarbamic acid and N,N-3-thiapentamethylenecarbamic acid.

Alkyl" whenever used above preferably indicates lower alkyl, containing up to 7 carbon atoms.

Acids which may be used in the quaternary salts defined above may be any conventional quaternisation acids which lead to pharmaceutically acceptable salts, for example HX (where X is halogen) and toluenesulphonic acids.

The methods that can be used to prepare the compounds of formula I depend to some extent upon the nature of R by way of example the following typical methods are shown:

a. by reaction of a xanthydrol or thiaxanthydrol of formula XnOH (or an ester thereof) with a compound of formula II Hil 33 3 NR R I b. by reaction of a compound of formula III XnNCX III with a hydrazine of formula IV R NI-I NR R C. by reaction of a compound of formula V XI'ICONg with a hydrazine of formula IV; d. by reaction of a compound of formula VI *3 i1 Xn.N C X VI wherein X is halogen, with a hydrazine of formula IV.

Obvious chemical equivalents (in this type of reaction) of compounds of formula V I may also be used, such as compounds of formula VI wherein X is N NCX or X -acy[l;

e. by reaction of a compound of formula VII 1 Xn Y VII

with a compound of formula VIII x R 3 Z-N--C--N--NRR VIII 1 ill Xn 1i x H IX with a hydrazine of formula IV; preferred esters include those of formulae X and XI R O I 1 II Xn-N-C-S--Pheny1 X v n Xn N C ON (lower alkyl) XI;

g. by reaction of a compound of formula XII XII XII

with a carbazoylating or thiocarbazoylating agent capable of providing the 61 NR NR R group; examples of such agents, which are chemical equivalents in this type of reaction, are the following: 1. an ester of a compound of formula XIII 3 2 R R N N C X H XIII,

a preferred ester is R R N-N(R )C(O)S-Phenyl; 2. a compound of formula XIV X R II 1 I 2 X C N NH R XIV wherein X is halogen or an obvious chemical equivalent (in this type of reaction) such as N NCX or X -acyl;

3. a compound of formula XV 1'1 NR R R llli C 3 4 XV and (4) a compound of formula XVI I31 I51 I32 XVI NO -N--C--N-NR. R v

h. by reduction of a compound of formula XVII XVII,

by conventional means, for example by hydrogenation in the presence of standard catalysts such as platinum, palladium, and the like, to give a compound of formula I wherein R, is hydrogen;

i. by reduction of a compound of formula XVIII R X R Il I j. by reductive alkylation of a compound of formula XIX R x R I I Xn N c N NH XIX by conventional means, for example using an an aldehyde or ketone of formula R COR (wherein R is alkyl and R is hydrogen or alkyl) and hydrogen in the presence of astandard catalyst such as platinum, palladium, and the like, to give compounds of formula I wherein R is hydrogen and R is alkyl.

k. by alkylation, alkanoylation or alkoxycarbonylation by conventional means of a compound of formula I in which at least one of R is a hydrogen atom to give the corresponding N-alkyl, N-alkanoyl or N-alkoxycarbonyl compound.

I. by N-alkanoylation, N-alkoxycarbonylation or O- acylation by conventional means of a compound of formula I containing an NI-I or OH group to give the corresponding N-alkanoyl, N-alkoxycarbonyl or O-acyl compound;

m. by dealkanoylation, dealkoxycarbonylation or deacylation of a compound of formula I containing an N-alkanoyl, N-alkoxycarbonyl or O-acyl group respectively to give the corresponding NI-I or -OH compound;

n. by alkylation or trialkylsilylation of a compound of formula I containing an OH group to give the corresponding alkoxy or trialkylsilyloxy compound;

0. by hydrogenolysis of a compound of formula XX NR R XX is benzyl, but chemical equivalents (in this type of reaction) of this group will be readily apparent to the skilled chemist; examples include methyl substituted by 2 or 3 phenyl groups, methyl substituted by l, 2 or 3 p-nitrophenyl, p-methoxyphenyl or 4- pyridyl groups, alkylsulphonyl, arylsulphonyl, arylthio, substituted arylsulphonyl and substituted arylthio; hydrogenation is carried out by conventional means in the presence of standard catalysts such as platinum, palladium, and the like;

p. by reaction ofa compound of formula I wherein R and R each represent alkyl, substituted alkyl, or alkenyl or together form a ring as hereinbefore defined with a conventional quaternising agent such as an alkyl halide, an alkyl p-toluene sulphonate, and the like, to form a pharmaceutically acceptable quaternary salt;

q. by reduction by conventional means of a compound of formula XXI R2 Xn-N-C N NO XXI xn' i1 co NH XXII with a hydrazine of formula IV; and

t. by reaction of a compound of formula XVIII with a compound of formula XXIII R Mg x XXIII in which R is lower alkyl and X is halogen.

We have found that compounds of formula I are antisecretory agents, with a specific activity against gastric secretion and without any anticholinergic activity. In particular the compounds reduce or inhibit the secretion of gastric acid in animals; they are therefore useful for reducing or inhibiting gastric secretion (particularly the secretion of gastric acid) and for the treatment of peptic ulceration. (The term peptic ulceration is used in its broad sense, as is conventional in the art, to include both gastric ulceration and duodenal ulceration).

The dosage rates of compounds of formula I vary according to the values of R but normally fall within the range /;-6O mg. of compound of formula I per kilogram of body weight of subject, preferably administered daily; in the cases of the more active compounds, dosage rates of 0.5-8 mg./kg. are acceptable. The antisecretory activity of the compounds, which has been demonstrated in the stimulated, pylorus ligated rat, has been found to be better in compounds of formula I wherein X, and X are oxygen than in similar compounds wherein X, and X are sulphur; substitution in rings A and B in general reduces activity.

The compounds of formula I may be administered orally, rectally or parenterally, preferably orally, the optimum dose rate varying with the activity of the compounds. A preferred dosage rate for oral administration is of the order of 25 mg. 4 g. daily, preferably 35 mg. 600 mg. daily, optionally in divided doses.

According to a further feature of the invention there are provided therapeutic compositions which comprise a compound of formula I in association with pharmaceutical excipients known for the production of compositions suitable for oral, rectal or parenteral administration. The compositions preferably contain 0.1 by weight of a compound of general formula I.

Compositions for oral administration are the preferred compositions of the invention, and these are the known pharmaceutical forms for such administration, such as for example tablets, capsules, syrups and aqueous and oily suspensions.

The excipients used in the preparation of these compositions are the excipients known in the pharmacists art.

Preferred compositions are tablets wherein a compound of formula I is mixed with a conventional inert diluent such as lactose in the presence of disintegrating agent, e.g., maize starch and lubricating agents, e.g., magnesium stearate. Such tablets may, if desired, be provided with enteric coatings by known methods, for example by the use of cellulose acetate phthalate. Similarly capsules, for example hard or soft gelatin capsules, containing a compound of formula I, with or without other excipients, may be prepared by conventional means and, if desired, provided with enteric coatings in known manner. The tablets and capsules may conveniently each contain 25-500 mg. of a compound of formula I. Other, but less preferred, compositions for oral administration include for example aqueous suspensions containing a compound of formula I in aqueous media in the presence of a non-toxic suspending agent e.g. sodium carboxymethylcellulose and dispersing agents, and oily suspensions containing a compound of formula I in a vegetable oil for example arachis oil.

Compositions of the invention suitable for rectal administration are the known pharmaceutical forms for such administration, such as for example suppositories with cocoa butter or polyethylene glycol bases.

Compositions of the invention suitable for parenteral administration are the known pharmaceutical forms for such administration, for example sterile suspensions in aqueous and oily media or sterile solutions in propylene glycol.

In the compositions of the invention the compounds of formula I may if desired be associated with other compatible pharmacologically active ingredients. For example antacids and acid adsorbents such as aluminium hydroxide and magnesium trisilicate may be included in compositions for oral administration to give an immediate antacid effect. Other pharmacologically active agents which may be associated with the compounds of formula I include compounds active on the central nervous system, including short and long acting sedatives such as the barbiturates and methaqualone, antihistaminic and/or antiemetic agents such as cyclizine and diphenhydramine, and anticholinergic agents such as atropine.

Milk and milk solids are valuable in the treatment of peptic ulcer, and the compositions of the invention in- Z-methyl-1,1pentamethylene-4-(9-thiaxanthenyl)- semicarbazide 4-( 2-hydroxy-9-thiaxanthenyl )-l l 3-oxapentamethylene)-semicarbazide 1-ethyl-'1-methyl-4-hydroxy-4-(9-xanthenyl)semicarbazide 1,l-hexamethylene-4-(9-thiaxanthenyl)semicarbazide 4-hydroxy-1,2-tetramethylene-4-(9-xanthenyl)- semicarbazide N-hydroxy-N-trimethylammonio-N-9- xanthenylurea iodide N -acetoxy-N-trimethylammonio-N -9- xanthenylurea iodide 4-( 1-chloro-9-xanthenyl)-4-hydroxy-1 1 -dimethy1- semicarbazide 4-( 1-f1uoro-9-xantheny1 )-4-hydroxy- 1 l -dimethylsemicarbazide 4-(2-fluoro'9-xanthenyl)-4-hydroxy-1,l-dimethylsemicarbazide 4-( l-chloro-9-xanthenyl)semicarbazide 4-( 1-fluoro-9-xanthenyl)semicarbazide 4-(2-fluoro-9-xanthenyl)semicarbazide 4-hydroxy-1,1-dimethyl-4-(1-methyl-9-xanthenyl)- semicarbazide 4-hydroxy-4-(1-methoxy-9-xanthenyl)-1,l-dimethylsemicarbazide 4-hydroxy-4-( 1 -hydroxy-9-xanthenyl 1 1 -dimethylsemicarbazide 4-(1-methy1-9-xanthenyl)semicarbazide 4-( 1-methoxy-9-xanthenyl)semicarbazide 4-( 1-hydroxy-9-xanthenyl)semicarbazide 4-B-methoxycarbonylpropionoxy-1,1-dimethy1-4-(9- xanthenyl)semicarbazide 1,1-dimethyl-4-methy1thioacetoxy-4-(9xanthenyl)- semicarbazide 1,1-dimethyl-4-pheny1acetoxy-4-(9-xanthenyl)- semicarbazide 1,1-dim ethy1-4-phenoxyacetoxy-4-( 9-xanthenyl) semicarbazide The above illustrates various values of A, B, X X and R in various combinations but of course it is to be understood that these values are not limited to the combinations named; all possible combinations are within the invention and each value of A, B, X X and R, is to be considered as having been exemplified generically, independent of any particular combination of radicals.

The acyl moiety of the typical acyloxy compounds listed may of course be replaced by other acyl groups as hereinbefore defined. Examples of acyl groups are the following:

Alkanoyl, e.g., acetyl, propionyl, butyryl, valeryl, octanoyl, stearyl, pivaloyl, ethoxalyl; substituted alkanoyl, e.g., phenylalkanoyl such as phenylacetyl; substituted phenylalkanoyl containing substituents such as halogen, alkyl, alkoxy, hydroxy, amino, alkylamino, acylamino, dialkylamino or nitro in the phenyl ring; phenoxyalkanoyl such as phenoxyacetyl; substituted phenoxyalkanoyl containing substituents such as halogen, alkyl, alkoxy, hydroxy, amino, alkylamino, acylamino, dialkylamino, or nitro in the phenyl ring; haloalkanoyl such as beta-chloropropionyl; alkoxyalkanoyl such as methoxyacetyl; alkylthioalkanoy] such as methylthioacetyl; dialkylaminoalkanoyl such as diethylaminoacetyl; acyl alkanoyl such as acetoacetyl; cycloalkyl alkanoyl such as cyclohexylacetyl; carboxyalkanoyl such as beta-carboxypropionyl, carboxyalkenoyl such as beta-carboxyacryloyl, and similar groups in ester or salt forms; heterocyclic alkanoyl such as pyridineacetyl;

alkenoyl, e.g., crotonyl;

cycloalkanoyl, e.g., cyclohexylcarbonyl;

aroyl, e.g., benzoyl, naphthoyl, substituted benzoyl in which the phenyl ring contains substituents such as halogen, alkyl, alkoxy, hydroxy, amino, alkylamino, acylamino, dialkylamino, nitro or carboxyl (and esters and salts thereof);

residues of carbonic acid, e.g., alkoxycarbonyl such as methoxycarbonyl, ethoxycarbonyl; substituted alkoxycarbonyl such as Z-methoxyethoxycarbonyl, Z-phenoxyethoxycarbonyl, 2-chloroethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl; alkenyloxycarbonyl such as allyloxycarbonyl; cycloalkoxycarbonyl such as cyclohexyloxycarbonyl; aryloxycarbonyl such as phenoxycarbonyl and similar groups containing halogen, alkyl, alkoxy, hydroxy, amino, alkylamino, acylamino, dialkylamino or nitro substituents in the phenyl ring; aralkoxycarbonyl such as Z-phenylethoxycarbonyl;

N-substituted carbamoyl, e.g., N-alkylcarbamoyl such as N-methylcarbamoyl; N,N-dialkylcarbamoyl such as N,N-dimethylcarbamoyl; N-phenylcarbamoyl; N,N-tetramethylenecarbamoyl; N,N-pentamethylenecarbamoyl; N,N-3-oxapentamethylenecarbamoyl; N,N-3-thiapentamethylenecarbamoyl;

heterocyclic carbonyl, e.g., groups comprising a carbonyl radical attached to a 5 7 membered heterocyclic ring containing up to two hetero atoms selected from oxygen, sulphur and nitrogen, such as thiophen, tetrahydrothiophen, furan, tetrahydrofuran, pyridine, benzothiazole, benzofuran, xanthen, pyrimidine.

The following non-limitative examples illustrate the invention.

EXAMPLE 1 A solution of xanthydrol (4 g.) and 1,1-dimethy1- semicarbazide (2 g.) in ethanolic acetic acid (1:1, 50 ml.) was left overnight at room temperature. After dilution with ice/water, the solid obtained was recrystallised from chloroform/petroleum ether b.p. 4060C. to give l,1-dimethyl-4-(9-xanthenyl)semicarbazide, m.p. 187-188C.

In a similar manner using the appropriate semicarbazide or thiosemicarbazide in place of 1,1-dimethylsemicarbazide, and the appropriate xanthydrol or thiaxanthydrol, there were prepared: 1,1-pentamethylene-4-( 9-xanthenyl)semicarbazide,

m.p. 202-202.5C. (from chloroform/petroleum ether b.p. 40-60C. 2-methyl-1,1-pentamethy1ene-4-(9-xanthenyl)semicarbazide, m.p. l53155C. (from petroleum ether b.p.

62-68C., and a trace of chloroform) 1, l-tetramethylene-4-(9-xantheny1)semicarbazide,

m.p. 203-206C. (from chloroform/petroleum ether b.p. 4060C.

1 ,1-hexamethy1ene-4-(9-xanthenyl)semicarbazide,

m.p. 201202C. (from chloroform/petroleum ether b.p. 40-60C.

1 ,1-diethyl-4-(9-xantheny1)semicarbazide, m.p. 164-168C. (from chloroform/petroleum ether b.p. 40-60C.

184185C. (from ethyl acetate) 4-( l-chloro-9-xanthenyl)- 1 1 -dimethylsemicarbazide,

m.p. 217219C. (from acetone) l,1-dimethyl-4-( 1-methyl-9-xanthenyl)semicarbazide,

m.p. 222223C. (from acetone) 1, l 3-methylazapentamethylene)-4-( l-methoxy-9- xanthenyl)-semicarbazide, In.p. 223224C. (from aqueous methanol) 1,1-( 3-methylazapentamehtylene )-4(4-methoxy-9- xanthenyl)-semicarbazide, m.p. 201-202C. (from methanol) 1 ,1-(3-methylazapentamethylene)-4-(9-thiaxanthenyl)-semicarbazide, m.p. 200202C. methanol) 1,1-(3-oxapentamethylene)-4-(9-thiaxanthenyl)' semicarbazide, m.p. 222224C. (from ethanol) The l-methoxyxanthydrol used as starting material in one of the above preparations was prepared as follows.

A mixture of l-methoxyxanthone (5.5 g.), 3.5% w/w sodium amalgam (60 g.) and ethanol (20 ml.) was boiled under reflux with stirring for 2 hours, and then cooled to room temperature. The organic layer was decanted from the mercury and diluted with 40 ml. ice water. The resulting precipitate was collected by filtration and dried to give l methoxyxanthydrol, m.p.

In a similar manner there was prepared the starting material 4-methoxyxanthydrol, rn.p. 122-123C.

EXAMPLE 2 A solution of N-methyl-N-9-xanthenylcarbamoyl chloride (1.95 g.) in toluene (20 ml.) was added to an ice-cooled solution of N,N-dimethylhydrazine (0.9 g.) in dry ether (10 ml.). After stirring for minutes at 0C the reaction mixture was washed with aqueous sodium bicarbonate and water, dried and evaporated. Recrystallisation of the residue from benzene gave 1,1 4-trimethy1-4-(9-xanthenyl)semicarbazide, m.p. 120123C.

in a similar manner using the appropriate carbamoyl chloride and hydrazine hydrate, the following compounds were prepared: 4-rnethyl-4-(9-xanthenyl)semicarbazide, m.p.

l46148C. (from chloroform/petroleum ether b.p.

(from 4-methoxy-4-(9-xantheny1)semicarbazide, m.p.

14l-143C. (from chloroform/ether) 4-isopropoxy-4-( 9-xanthenyl)semic arbazide, mp

semicarbazide, m.p. 178l80C. (from ethyl acetate) N-Methyl-N-9-xanthenylcarbamoyl chloride was prepared by adding a mixture of N-methyl-9- xanthenylamine (10 g.), triethylamine (7 m1.) and dry toluene ml.) to a 10% solution of phosgene in toluene (250 ml.) at about 17C. After overnight standing, the reaction product was evaporated at less than 30C. under reduced pressure to dryness. The residue was boiled with petroleum ether (b.p. 6268C.), triethylamine hydrochloride filtered off, and the filtrate crystallised to give N-methyl-N-9-xanthenylcarbamoyl chloride, m.p. 9495C.

N-Methoxy-N-9-xanthenylcarbamoyl chloride was prepared by adding a mixture of N-methoxy-N-9- xanthenylamine (7 g.), triethylamine (9 ml.) and toluene (10 ml.) to a 10% solution of phosgene in toluene (93 ml.) at l5C. to -l0C. The reaction mixture was stirred at 10C. for 15 minutes and then allowed to attain room temperature over 1 hour. Evaporation in vacuo after filtering from triethylamine hydrochloride gave crude N-methoxy-N-9-xanthenylcarbamoyl chloride in the form of a yellow-brown oil. This was used dissolved in toluene.

N-lsopropoxy-N-9-xanthenylcarbamoyl chloride was prepared in a similar manner in the form of a brown oil, and this was used dissolved in toluene.

EXAMPLE 3 a. A solution of S-phenyl Nhydroxy-N-9-xanthenylthiocarbamate (1.7 g.) in pyridine (12.5 ml.) containing triethylamine (0.4 ml.) was treated with hydrazine hydrate (0.78 ml.) at room temperature and left for 4 hours. After heating on the steam bath for 1 hour and overnight standing at room temperature, the reaction mixture was diluted with water (35 m1.) and filtered. The filtrate was diluted with a large volume of water; the resulting precipitate was crystallised from dimethylformamide/toluene to give 4-hydroxy-4-(9-xantheny1)- semicarbazide, mp. 186C.

In a similar manner using S-phenyl N-9-xanthenylthiocarbamate in place of S-phenyl N-hydroxy-N-9- xanthenylthiocarbamate, there was prepared 4-(9-xanthenyl)semicarbazide, m.p. 2122l4C. (from dimethylformamide/toluene).

In a similar manner using S-phenyl N-9-xanthenylthiocarbamate and methylhydrazine, there was obtained 2-methyl-4-(9-xanthenyl)semicarbazide, m.p. 183-186C. (from benzene).

The starting thiocarbamates were prepared as follows. S-Phenylthiocarbonyl chloride (2.8 ml.) was added to a stirred solution of N-9-xanthenylhydroxylamine (2.13 g.) in pyridine (10 ml.) at 0C. After overnight standing at 0C., the reaction mixture was diluted with water ml.). The product was isolated in ether (washing with fresh 5% aqueous sodium carbonate) and crystallised from acetone/petroleum ether b.p. 6268C. to give S-phenyl N-hydroxy-N-9-xanthenylthiocarbamate, m.p. l77l 78C.

In a similar manner using N-9-xanthenylamine in place of N-9-xanthenylhydroxylamine, there was prepared S-phenyl N-9-xanthenylthiocarbamate, m.p. 185-187C. (from acetone).

b. O-Chloroformyl ethyl methyl ketoxime (3.3 g.) was added dropwise to a solution of N-9-xanthenylhydroxylamine (4.26 g.) in dry pyridine (20 ml.) at 0C., and allowed to stand for 1 hour to give a crude solution of ethyl methyl ketoxime N-hydroxy-N-9-xanthenylcarbamate. 5M1. of this was treated with hydrazine hydrate recrystallised from dimethylformamide/toluene to give 4-hydroxy-4-(9-xanthenyl)semicarbazide m.p. 184C.

0. Ethyl N-9-xanthenylcarbamate (l g.) and N,N-dimethylhydrazine (ml.) were added to a solution of sodium (0.1 g.) in methanol ml.). The mixture was sealed in a pressure vessel and heated at 100C. for 18 hours, after which time it was evaporated to dryness. Recrystallisation from benzene and then carbon tetrachloride gave 1,1-dimethyl-4-(9-xanthenyl)semicarbazide, m.p. l89191C.

cl. Hydrazine hydrate (0.82 ml.) was added to a solution of S-phenyl N-9-thiaxanthenylthiocarbamate (679 mg.) in pyridine (7 ml.) containing triethylamine (1.4 ml.) at 0C. After 3 hours at 0C., the reaction mixture was diluted with ice/water (50 ml.) and the resulting precipitate recrystallised from chloroform/petroleum ether b.p. 62-68C. to give 4-(9-thiaxanthenyl)- semicarbazide, m.p. 199201C.

S-Phenyl N-9-thiaxanthenylthiocarbamate (m.p. 16ll65C. ex acetone/petroleum ether b.p. 62-68C.) was prepared from S-phenyl-thiocarbamoyl chloride and 9-thiaxanthenylamine in a manner similar to that described in (a) for S-phenyl N-hydroxy-N-9- xanthenylthiocarbamate.

EXAMPLE 4 S-Phenylthiocarbonyl chloride (6 ml.) in dioxan (20 ml.) was added dropwise to a stirred, ice-cooled solution of N,N-dimethylhydrazine (5.04 g.) in dioxan (60 ml.). After stirring at 0C. for minutes, the mixture (containing S-phenyl N,N-dimethylthiocarbazate) was filtered into a stirred solution of N-9-xanthenylhydroxylamine (8.96 g.) in pyridine (136 ml.) containing triethylamine (6.4 ml.) at room temperature. After 24 hours, the reaction mixture was diluted with water, and the resulting precipitate recrystallised from dimethylformamide/toluene to give 4-hydroxy-l,1-dimethy1-4- (9-xanthenyl)semicarbazide, m.p. l98200C.

In a similar manner using N-9-thiaxanthenylhydroxylamine in place of N-9-xanthenylhydroxylamine, there In a similar manner using l-amino-4-methylpipera- 'drazine, there was prepared 1,1-hexamethylene-4- hydroxy-4-(9-xantheny1)semicarbazide,

m.p. 172.5-173C. (from methanol).

In a similar manner using N-(1-methoxy-9-xanthenyl)-hydroxylamine [m.p. 153155C. (from benzene), prepared by reacting l-methoxyxanthydrol with hydroxylamine hydrochloride in aqueous dioxan, followed by liberation of the free base by the addition of aqueous sodium acetate] in place of N-9-xanthenylhydroxylamine and 1-amino-4-methylpiperazine in place of N,N-dimethylhydrazine, there was prepared 4- hydroxy-4-( 1-methoxy-9-xanthenyl)-l ,1-(3- methylazapentamethylene)semicarbazide, 143151C. (from aqueous methanol).

In a similar manner using N-(1-methyl-9-xanthenyl)- hydroxylamine (prepared. by reacting 1- methylxanthydrol with hydroxylamine hydrochloride in aqueous dioxan at room temperature, followed by liberation of the free base by addition of aqueous sodium acetate solution) in place of N-9-xanthenylhydroxylamine and l-amino-4-methylpiperazine in place of N,N-dimethylhydrazine, there was prepared 4- hydroxy-4-( l-methyl-9-xanth.enyl)-1,l-(3- methylazapentamethylene)semicarbazide, 182l 83C. (from ethanol).

In a similar manner using 'N-9-thiaxanthenylhydroxylamine in place of N-9-xanthenylhydroxylamine and N-aminopiperidine in place of N-N-dimethylhydrazine, there was prepared 4-hydroxy-l,1-pentamethylene-4- (9-thiaxanthenyl)semicarbazide, m.p. 150C. (from chloroform/petroleum ether b.p. 60-80C.).

In a similar manner using N-9-thiaxanthenylhydroxylamine in place of N-9-xan.thenylhydroxylamine and 4-aminomorpholine in place of N,N-dimethylhydrazine, there was prepared 4-hydroxy-l,1-(3- oxapentamethylene)-4-(9-thiaxanthenyl)semicarbazide, m.p. 152-153C. (from dimethylformamide/toluene).

In a similar manner using N-9-thiaxanthenylhydroxylamine in place of N-9-xanthenylhydroxylamine and l-amino-4-methylpiperazine in place of N,N-dimethylhydrazine, there was prepared 4-hydroxy-1,1-(3- methylazapentamethylene)-4l-(9-thiaxanthenyl)- semicarbazide, m.p. C. (from chloroform/light petroleum b.p. 6080C.).

In a similar manner using N-9-xanthenylamine in place of N-9-xanthenylhydroxylamine and 4- aminomorpholine in place of N,N-dimethylhydrazine, there was prepared 1,1-(3-oxapentamethylene)-4-(9- xanthenyl)semicarbazide, m.p. 205-207C. (from methanol).

In a similar manner using N-methyl-9- xanthenylamine in place of N-9-xanthenylhydroxylamine and N-aminohexame'thylenimine in place of N,N-dimethylhydrazine, there was prepared 1,1- hexamethylene-4-methyl-4-(9-xanthenyl)- semicarbazide, m.p. 147l48C. (from ethyl acetate). In a similar manner the following preparation was carried out. S-Phenylthiocarbonyl chloride (1.23 ml.) in tetrahydrofuran (6 ml.) was added dropwise during 30 minutes to a stirred, ice-cooled suspension of N- aminopyrrolidine hydrochloride (1.1 g.) in tetrahydrofuran (9 ml.) containing triethylamine (1.82 ml.). The mixture was stirred for 2 hours with the coolant removed, and then filtered. The filtrate was added to a solution of N-methyl-9-xanthenylamine (1.27 g.) in pyridine (3 ml.) containing triethylamine (0.91 ml.) and the resulting solution boiled under reflux for 2 hours. The resulting solution was shaken with a mixture of water (30 ml.) and petroleum ether (b.p. 62-68C.,

7.5 ml.). The organic layer was separated and evaporated below 30C. in vacuo using a rotary evaporator. The resulting yellow oil was triturated with ether to give a solid which was crystallized from acetone to give 4-methyl-1,1-tetramethylene-4-(9-xanthenyl)semicarbazide, m.p. 122-124C.

EXAMPLE 4-(9-Xanthenyl)semicarbazide (0.59 g.) in pyridine ml.) was treated with acetic anhydride (0.6 ml.) and left at room temperature for 24 hours. Dilution with water (200 ml.) and recrystallisation of the precipitate obtained from dimethylformamide/toluene gave -acetyl-4-(9-xanthenyl)semicarbazide, m.p. 226228C.

EXAMPLE 6 A solution of 4-hydroxy-l,l-dimethyl-4-(9-xanthenyl)-semicarbazide (897 mg.) in pyridine (10 ml.) was treated with acetic anhydride (612 mg.) and left at room temperature for 24 hours. Dilution with ice/water (100 ml.) and crystallisation of the resulting precipitate from acetonel-petroleum ether b.p. 6268C. gave 4- acetoxy- 1 ,1-dimethyl-4-( 9-xanthenyl )semicarbazide, m.p. 120l2lC.

In a similar manner using propionic anhydride in place of acetic anhydride there was obtained 1,1- dimethyl-4-propionyloxy-4-(9-xanthenyl)semicarbazide, m.p. l23-124C. (from acetone/petroleum ether b.p. 40-60c.).

In a similar manner using isobutyric anhydride there was obtained 4-isobutyryloxy-1,l-dimethyl-4-(9-xanthenyl)-semicarbazide, m.p. 13l132C. (from acetone).

In a similar manner using butyric anhydride there was obtained 4-butyry10xy-l,1-dimethyl-4-(9-xanthenyl)- semicarbazide, m.p. l1l7C. (from acetone/petroleum ether b.p. 6268C.).

In a similar manner using hexanoic anhydride there was obtained 4-hexanoyloxy-l,l-dimethyl-4-(9-xanthenyl)-semicarbazid'e.

In a similar manner there were obtained:

4-acetoxy-1,1-(3-oxapentamethylene)-4-(9-xanthenyl)-semicarbazide, m.p. 148C. (from acetone/hexane).

4-acetoxy-l ,1-(3-methylazapentamethylene)-4-(9- xanthenyl)-semicarbazide, m.p. 141C. (from acetone/hexane EXAMPLE 7 A solution of 4-acetoxy-1,l-dimethyl-4-(9-xanthenyl)-semicarbazide (143 mg.) in methanol (5 ml.) was treated with 1N sodium hydroxide solution (0.63 ml.) and left at room temperature for 2 hours. Acetic acid (0.05 ml.) was then added and the reaction mixture diluted with water (5 ml.). The resulting precipitate was dried to give 4-hydroxy-l,1-dimethyl-4-(9- xanthenyl)semicarbazide, m.p. 196l98C.

In a similar manner, crude 4-acetoxy-1-acety1-4-(9- xanthenyl)semicarbazide (prepared by the method of Example 6 from 4-hydroxy-4-(9-xanthenyl)semicarbazide) was hydrolysed to give l-acetyl-4-hydroxy-4-(9- xanthenyl)-semicarbazide, m.p. l73176C. (from dimethylformamide/-toluene).

EXAMPLE 8 Xanthen-9-carbonyl azide (4 g.) in benzene (50 ml.)

was warmed to 5060C. until nitrogen evolution ceased. To the filtered solution (containing 9- xanthenyl isocyanate) there was added ethoxycarbonylhydrazine (1.67 g.) in' benzene (10 ml.). After 1 hour, the reaction product was filtered and the residue recrystallised from dimethylformamide/toluene to give 1-ethoxycarbonyl-4-(9-xantheny1)semicarbazide, m.p. 18819lC.

In a similar manner, using methylhydrazine and N,N-dimethylhydrazine in place of ethyoxycarbonylhydrazine, there were obtained respectively 2-methy1- 4-(9-xanthenyl)-semicarbazide, m.p. 188190C. (from methanol) and l,2-dimethyl-4-(9-xanthenyl)- semicarbazide, m.p. l 18l 19C.

In a similar manner, using l-amino-4-methylpiperazine in place of ethoxycarbonylhydrazine, there was obtained:

1 ,1-(3-methylazapentamethylene)-4-(9-xanthenyl)- semicarbazide, m.p. 214-215C. (from ethyl acetate).

Xanthene-9-carbonyl azide used above was prepared as follows. Xanthen-9-carbonyl chloride [6.65 g., m.p. 8790C., prepared by refluxing xanthen-9-carboxylic acid (6.34 g.) with thionyl chloride (25 ml.) for 2 hours and evaporating to dryness] was dissolved in acetone (25 ml.) and stirred in an ice bath. Sodium azide (2.5 g.) in water (10 ml.) was added slowly at 12-17C., and then water (10 ml.) was added to the mixture at 10C. The precipitate thus obtained was filtered off, washed with cold 50% aqueous acetone (20 ml.) and dried. It was then recrystallised from ether at C. to give xanthen-9-carbonyl azide, decomposition point 72C.

EXAMPLE 9 Xanthen-9-carbonyl azide (l g.) and N,N-dimethylhydrazine (0.4 ml.) in dry benzene (15 ml.) were wanned to 60C., causing an effervescence which was complete in 30 minutes. After 1 hour at 25C., the precipitate was collected to give 1,1-dimethyl-4-(9-xanthenyl)semicarbazide, m.p. 189195C.

EXAMPLE 10 Acetone 4-(9-xanthenyl)semicarbazone (274 mg.) in methanol (38 ml.). acetic acid (1 ml.) and water (1 ml.) was treated with hydrogen in the presence of platinum oxide (25 mg). When reduction was complete, the reaction mixture was filtered, the filtrate evaporated to dryness, and the residue recrystallised from benzene to give l-isopropyl-4-(9-xanthenyl)semicarbazide, m.p. 161.5-.162.5C.

EXAMPLE 1 1 4-Benzyloxy-l,1-dimethyl-4-(9-xanthenyl)semicarbazide (389 mg.) in ethanol (25 ml.) was treated with hydrogen in the presence of 10% palladium charcoal (80 mg). When hydrogenation was complete, the reaction mixture was filtered, the product washed from the catalyst with dimethylformamide 10 ml.) and the solution evaporated to dryness in vacuo. The residue was recrystallised from dimethylformamide/toluene to give 4-hydroxy-1,1-dimethyl-4-(9-xanthenyl)semicarbazide, m.p. 192193C.

In a similar manner from the appropriate 4- benzyloxy-4-(9-xanthenyl)semicarbazide, there were prepared:

17 1,l-diethyl-4-hydroxy-4-(9-xanthenyl)semicarbazide,

(from dimethylformamide) m.p. 208C. 4-hydroxy1,1-dipropyl-4-(9-xanthenyl)semicarbazide,

m.p. 198C. (from dimethylformamide) 4-hydroxy-1,1-pentamethylene-4-(9xanthenyl)- semicarbazide, m.p. 192C.

(from dimethylformamide/toluene/petroleum ether b.p. 6080C. 1:1:1). 4-hydroxy-4-(9-xanthenyl)semicarbazide, m.p. 185C. (from dimethylformamide/toluene/petroleum ether,

b.p. 6080C.) 4-hydroxy-1,l-tetramethylene-4-(9-xanthenyl)- semicarbazide, m.p. 176C. (from dimethylformamide) The starting materials were prepared as follows. A mixture of O-benzyl-N-9-xanthenylhydroxylamine (3.03 g.) and triethylamine (1 ml.) in dry toluene (30 ml.) was added dropwise to a 10% solution of phosgene in toluene (30 ml.) maintained at 20C. After minutes at this temperature and 1 hour to rise to room temperature, the reaction mixture was filtered and the filtrate evaporated in vacuo to give crude N-benzyloxy- N-9-xanthenylcarbamoyl chloride in the form of a brown oil. A solution of this material (about 1 equivalent) in toluene (30 ml.) was added to 1,1-dimethylhydrazine (0.6 g.), triethylamine (l g.) and toluene (30 ml.) at room temperature. After overnight stirring, the reaction mixture was filtered and the filtrate evaporated to dryness in vacuo. Recrystallisation of the residue from cyclohexane/petroleum ether b.p. 62-68C. gave 4-benzyloxy-1,1-dimethyl-4-(9-xanthenyl)- semicarbazide, m.p. 1 17C.

In a similar manner there were prepared: 4-benzyloxy-1,1-diethyl-4-(9-xanthenyl)semicarbazide, (from cyclohexane) m.p. 126.5-127.5C. 4-benzyloxy-l ,1-dipropyl-4-(9-xanthenyl)semicarbazide, m.p. 82C. (from chloroform/petroleum ether b.p. 62-68C.) 4-benzyloxyl ,1-pentamethylene-4( 9-xanthenyl semicarbazide m.p. 143-144C.(from chloroform- /petroleum ether b.p. 62-68C.) 4-benzyloxy-4-(9-xanthenyl)semicarbazide,

126C. (from ether) 4-benzyloxy-1,1-tetramethylene-4-(9-xanthenyl)- semicarbazide m.p. ll9120C. (from cyclohexane/petroleum ether, b.p. 6080C.)

EXAMPLE 12 A solution of l,1-dimethylsemicarbazide (1.03 g.) in dry dioxan (20 ml.) was stirred at room temperature for 3 hours with sodium hydride (0.48 g., 50% oil dispersion). 9-Chloroxanthen (2.16 g.) in dioxan (15 ml.) was added dropwise and, after overnight stirring, the mixture was poured into ice/water 100 ml.) containing saturated aqueous sodium bicarbonate (5 ml.). The resulting precipitate was boiled with benzene (20 ml.), cooled and the separated solid extracted with hot carbon tetrachloride (15 ml). On cooling there was obtained l, l -dimethyl-4-(9-xanthenyl )semicarbazide, m.p. 193-l94C.

EXAMPLE 13 Sodium hydride (0.48 g., 50% oil dispersion) was added to a solution of 1,l-dimethyl-4-(9-xanthenyl)- semicarbazide (2.83 g.) in tetrahydrofuran (40 ml.). After 2 hours under reflux, methyl iodide (1.32 ml.) was added and refluxing continued for 5 hours. Methanol (5 ml.) was then added to the cooled and filtered reaction mixture, and the solution evaporated to 10 ml. Chloroform (25 ml.) was added, the solution filtered and then evaporated. The portion of the residue insoluble in hot petroleum ether b.p. 40-60C. (2 X 15 ml.) was recrystallised from chloroform to give 1,1,2-

trimethyl-4-( 9-xanthenyl )semlicarbazide. m.p. 1 4 l-1 42C.

EXAMPLE 14 A suspension of N-methyl-N-nitroso-N xanthenylurea (520 mg.) and platinum oxide (1 10 mg.) in methanol (20 ml.) was shaken under hydrogen for 12 hours. After filtration, the reaction mixture was evaporated in vacuo to about 1.5 ml. and diluted with water. The precipitate was collected and the benzenesoluble portion crystallised from benzene and from benzene/petroleum ether b.p. 62-68C. to give 2- methyl-4-(9-xanthenyl)semicarbazide, m.p. l73l76C.

The starting material was prepared as follows. A suspension of N-methyl-N-9-xanthenylurea (5.08 g.) in acetic acid (75 ml.) and water (5 ml.) at 5C. was treated with a solution of sodium nitrite (1.52 g.) in water (5 ml.). After ice cooling, the precipitate was collected and recrystallised from ethanol and from benzene/petroleum ether b.p. 6268C. to give the required product, m.p. 151C.

EXAMPLE 15 A mixture of 1,1-dimethyl.-4-(9-xanthenyl)semicarbazide (259 mg.), methyl iodide (0.1 ml.) and acetone (10 ml.) was refluxed for 7 hours. After cooling, the precipitate was recrystallised from nitromethane to give N-trimethylammonio-N-9-xanthenylurea iodide, m.p. 196C.

In a similar way there were prepared the following compounds. 4-(3-hydroxy-3-9-xanthenylureido)-1,l-

dimethylpiperazinium iodide, m.p. 216C.

4-( 3-acetoxy-3-9 -xanthenylu:reido)- 1 ,1-

dimethylpiperazinium iodide, m.p. 203C.

4-( 3-9 '-xanthenylureido 1 1 -dimethylpiperazinium iodide, m.p. 259260C.

EXAMPLE 15A Thionyl chloride 1 ml.) was added dropwise to a solution of l-methylxanthydrol (2.0 g.) in dry ether (25 ml.). The mixture was boiled under reflux for 1.5 hours, cooled to room temperature, and filtered. The filtrate was evaporated to dryness to give 9-chloro-lmethylxanthen as a solid product. A mixture of this compound (2.0 g.), silver cyanate (2.6 g.) and dry ether 15 ml.) was stirred overnight at room temperature and then filtered through kieselguhr. One half of this fitrate (containing l-methyl-9- xanthenylisocyanate) was added dropwise to a stirred mixture of 1-amino-4-methylpiperazine (1 ml.) and tetrahydrofuran (5 ml.) The precipitate which formed was collected by filtration, washed with ether and recrystallized from toluene to give 1,1-(3- methylazapentamethylene)-4-( 1-methyl-9-xanthenyl)- semicarbazide, m.p. 21 l2 l 3C.

In a similar manner, using 4-aminomorpholine in place of l-amino-4-methylpiperazine, there was prepared 4-( l-methyl-9-xanthenyl)-1,1-(3-oxapentamethylene)semicarbazide, m.p. 215-216C. (from methanol). [Satisfactory elemental analyses were obtained for the compounds prepared in the above Examples. Structures were confirmed by infra red spectroscopy and, where necessary, by nuclear magnetic resonance spectroscopy In many cases, the compounds melted with decomposition at the temperatures described] EXAMPLE 16 In the preparation of tablets, mixtures of the following type may be tabletted in conventional manner:-

Compound of formula I I 90% Lactose 0 80% Maize starch Magnesium stearate ca. l7c

Microcrystalline cellulose O 90% (by weight) EXAMPLE 17 In the preparation of tablets the following mixture was dry granulated and compressed in a tabletting machine to give tablets containing 50 mg. of active ingredient:

4-hydroxyl l -dimethyl-4-( 9-xanthenyl) 25% semicarbazide Maize starch 10% Lactose Magnesium stearate 1% Microcrystallirle cellulose to 100% by weight EXAMPLE l8 In the preparation of enteric coated tablets, tablets prepared as described in Example 17 were coated with sanderac varnish and then coated with cellulose acetate phthalate using a solution of 20% cellulose acetate phthalate and 3% diethyl phthalate in a mixture of equal parts of industrial alcohol and acetone.

EXAMPLE 19 In the preparation of tablets the following mixture was dry granulated and compressed in a tabletting machine to give tablets containing 5 mg. of active ingredient:- 4-hydroxy- 1 l -dimethyl-4-( 9-xanthenyl)- semicarbazide (l0 g.), lactose 10 g.), and maize starch (5 g.).

EXAMPLE 20 In the preparation of enteric coated tablets, the tablets described in Example 19 were given a thin coat of shellac followed by 20 coats of cellulose acetate phthalate.

EXAMPLE 21 In the preparation of capsules, a mixture of the ingredients described in Example 19 was encapsulated in hard gelatin capsules. Enteric coating was applied by conventional dipping in cellulose acetate phthalate.

EXAMPLE 22 The following mixture was compressed into tablets in a conventional manner:

4-hydroxyl l -dimethyl-4'( 9-xanthenyl) 25% semicarbazide Sodium bicarbonate Peppermint oil q.s.

EXAMPLE 23 In the preparation of capsules a mixture of equal parts by weight of 4-hydroxy-1,l-dimethyl-4-(9-xanthenyl)-semicarbazide and lactose was encapsulated in hard gelatin capsules, each capsule containing 50 mg. of the semicarbazide.

EXAMPLE 24 In the preparation of enteric coated capsules, the capsules of Example 23 were coated with cellulose acetate phthalate in the conventional manner.

EXAMPLE 25 Suppositories weighing lg. and containing 50 mg. 4- hydroxy-l l -dimethyl-4-(9-xanthenyl)semicarbazide were prepared in conventional manner using a base consisting of Polyethylene glycol 4000 33% Polyethylene glycol 6000 47% Water 20% EXAMPLE 26 A solution for parenteral administration was prepared comprising 4-hydroxyl l -dimethyl-4-( 9-xanthenyl)semicarbazide, in propylene glycol, mg./2 ml. sterilised by filtration.

Compositions similar to those described in Examples 16 26 are also prepared, containing other compounds of formula I previously described in place of 4-hydroxyl,l-dimethyl-4-(9-xanthenyl)semicarbazide. These compounds of formula I include the following compounds: 4-hydroxyl l-pentamethylene-4-( 9-xanthenyl)- semicarbazide l, l -tetramethylene-4-(9-xanthenyl)semicarbazide l,1-(3methylazapentamethylene)-4-( l-methoxy-9- xanthenyl)semicarbazide l ,1-(3methylazapentamethylene)-4-(9-thiaxanthenyl)-semicarbazide I 1, l 3-oxapentamethylene )-4-( 9-thiaxanthenyl)- semicarbazide 4-hydroxyl l 3-oxapentamethylene)-4-( 9-xanthenyl )-semicarbazide 4-hydroxyl l 3-methylazapentamethylene )-4-( 9- xanthenyl)semicarbazide 4-hydroxyl ,1-pentamethylene-4-(9-thiaxanthenyl)- semicarbazide 4-hydroxyl l 3-oxapentamethylene )-4-( 9-thiaxanthenyl)semicarbazide l, l 3-oxapentamethylene )-4-(9-xanthenyl)semicarbazide 4-acetoxy-l l 3-oxapentamethylene )-4-( 9-xanthenyl )semicarbazide 21 l,l-( 3-methylazapentamethylene )-4-( 9-xanthenyl semicarbazide We claim: 1. A compound of formula I in which X is oxygen or sulphur; the rings A and B may optionally contain substituents selected from halogen, lower alkyl, lower alkoxy and hydroxy;

R, is hydroxy, lower alkoxy, lower alkanoyloxy, hy-

drogen or lower alkyl; R is hydrogen or lower alkyl; and R and R together with the nitrogen atom to which they are attached, form a saturated 5 7 membered heterocyclic ring, optionally containing an additional hetero group selected from O and N-lower alkyl;

together with pharmaceutically acceptable acid addition salts and pharmaceutically acceptable quaternary salts'of compounds of formula I. 2. A compound of formula IA (I R i '3 n i H' N C N NR5R4 22 in which R, is hydroxy, lower alkoxy, lower alkanoyloxy, hy-

drogen or lower alkyl;

R is hydrogen or lower alkyl; and

R and R together with the nitrogen atom to which they are attached, form a saturated 5 7 membered heterocyclic ring, optionally containing an additional hetero group selected from O and N lower alkyl;

together with pharmaceutically acceptable acid addition salts of compounds of formula IA.

3. A compound of formula IB R o R I II H N c N NR5R4 in which R is hydroxy, lower alkoxy, lower alkanoyloxy, hy-

drogen is lower alkyl;

R is hydrogen or lower alkyl; and

3 and R together with the nitrogen atom to which they are attached, form a saturated 5 7 membered heterocyclic ring, optionally containing an additional hetero group selected from O and ll- -ll ower alkyl;

together with pharmaceutically acceptable acid addition salts of compounds of formula IB.

4. The compound of claim 2 which is 4-hydroxy-l ,1- pentamethylene-4-( 9-xanthenyl)semicarbazide.

5. The compound of claim 2 which is tetramethylene-4-(9-xanthenyl)semicarbazide. 

1. A COMPOUND OF FORMULA 1
 2. A compound of formula IA
 3. A compound of formula IB
 4. The compound of claim 2 which is 4-hydroxy-1,1-pentamethylene-4-(9-xanthenyl)semicarbazide.
 5. The compound of claim 2 which is 1,1-tetramethylene-4-(9-xanthenyl)semicarbazide. 